1. Field of the Invention
This invention relates in general to magnetic recording disk drives, and more particularly to the configuration of the air bearing surface of a slider for use in a contact start/stop magnetic disk drive.
2. Description of Related Art
Disk drives are storage devices that use a rotatable disk with concentric data tracks containing information, a head or transducer for reading and/or writing data onto various tracks, and an actuator connected to a carrier for the head moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
In typical magnetic recording disk drives, the head carrier is an air bearing slider that flies above the disk surface and maintains a very thin air cushion when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The suspension provides a small load (e.g., a gram load) on the slider by spring stiffness, pushing the slider toward to the disk, but the air flow in the air bearing under the slider creates a force that tends to push the slider away from the disk. The spacing between the slider and rotating disk can be maintained by the balance of the two forces.
For contact start/stop (CSS) disk drives, the air bearing slider is in contact with the disk surface during start and stop operations when there is insufficient disk rotational speed to maintain the air bearing. To reduce wear between the disk and slider, a thin lubricant layer is placed over the surface of the disk. When a drive is turned off, the slider is typically brought to the inner radius of the disk to land on the disk surface. A dedicated textured landing area (or landing zone) is designated, typically at the inner radius of the disk surface, for the purpose of providing a landing surface for the slider and to minimize stiction. The structure of the landing zone texture can be formed by a laser tool, producing evenly spaced crater or half sphere shaped bumps with height of 130xcx9c150 xc3x85.
Stiction results when the air bearing surface (ABS) of the slider has been in stationary contact with the disk for a period of time and tends to resist translational movement or xe2x80x9csticksxe2x80x9d to the disk surface. Stiction is caused by a variety of factors, including static friction and adhesion forces between the disk and slider created by the thin film of lubricant. Excessively high stiction force can cause hard disk drive non-operable because the spindle motor current may not be enough to overcome the adhesion force between the slider and disk. Stiction can also result in damage to the head or disk when the slider suddenly breaks free from the disk surface when disk rotation is initiated. In addition, because the suspension between the actuator and the slider is relatively fragile to permit the slider to fly above the disk surface, sudden rotation of the disk can also damage the suspension. In general, landing zone bump height is one of the most important factors affecting stiction level (the higher the bump height, the lesser the stiction). Stiction can be further reduced by optimizing the shape, size, and density of the bumps in the landing zone.
The main problem with the imparting higher bump height of laser texture to the landing zone area of the disk is that it brings the disk surface that much closer to a flying head. The margin between the flying height and the top most region of the texture area is reduced, thereby increasing the potential for head disk contact and hence the possibility of a head crash. IBM""s U.S. Pat. No. 5,870,250 disclosed the use of different slider profiles having a single etch depth design to produce a fly height profile in which the slider typically flies higher over a textured landing zone than over a data zone of a disk. The slider profiles incorporate either a central rail or a side rail to achieve different fly height profiles. However, the fly heights achieved by the prior art ABS slider designs are not suitable for low fly height products due to its inability to fly low in addition to meeting other operating factors such as fly height sensitivity, altitude loss, and seek loss. As the pressure to increase recording density forces lower flying heights, the balance between maintaining bump height on the landing zone and the need to fly lower on the data zone is a difficult challenge. What is needed is an improved air bearing slider design that is capable of landing and clearing the texture landing zone while being able to maintain a flat fly height as close to the disk as possible.
The present invention overcomes the drawbacks of the prior art by configuring a dual depth slider air bearing surface having a novel rear pad and trailing ABS pad that enable the slider to achieve a ramp fly height profile near the textured landing zone of a disk. The air bearing slider structure includes a slider body on which a U-shaped leading ABS pad is defined near and along a leading edge (relative to a moving recording medium) and partially along each side of the slider body. A front pad extends from the leading edge section of the leading ABS pad to the leading edge of the slider body, at a reduced height relative to the height of the ABS pad. An asymmetric or skewed rear pad is defined along a centerline or longitudinal axis of the slider body and proximate to a trailing edge of the slider body. Extending above the rear pad is a trailing ABS pad. In accordance with one embodiment of the present invention, the trailing ABS pad has an asymmetric profile with respect to the longitudinal axis of the slider. The trailing ABS pad has a wider section (in the direction of the longitudinal axis) on one side of the longitudinal axis and a narrow section on another side of the longitudinal axis, with a curved bowing profile on the leading edge side of the trailing ABS pad.